1. Field of the Invention
This invention relates to a method of manufacturing a sealed-type nickel-hydrogen cell.
2. Prior Art
It has been said heretofore that a method for manufacturing a sealed-type nickel-hydrogen cell employing a hydrogen-occlusion alloy electrode has much in common with the method used to manufacture a nickel-cadmium cell, so that it is possible to divert the existing manufacturing facilities of the latter to the manufacturing of the former. Such diversion is advantageous in terms of equipment investment.
In one example of a method for manufacturing a sealed-type nickel-hydrogen cell, a well-known paste-type nickel electrode plate and a paste-type hydrogen electrode plate are stacked in a laminated fashion with a separator placed therebetween, and rolled up together and inserted into a cylindrical can. An aqueous solution of 7N KOH, as an electrolyte, is then put into the can and a lid is then attached thereto by caulking to provide an airtight sealing of the can. This sealed-type cylindrical nickel-hydrogen cell so fabricated is subjected to a formation process in which it is charged and discharged for the formation treatment of both the nickel and the hydrogen electrode plates.
In another example of the sealed-type nickel-hydrogen cell, the paste type nickel electrode and hydrogen electrode plate are also stacked in a laminated fashion with a separator placed therebetween and are inserted flat into a square can. An aqueous solution of 7N KOH, as an electrolyte, is put into the can and a lid is then attached thereto by means of laser welding to hermetically seal the can. This square sealed-type nickel-hydrogen cell so fabricated is subjected to a formation process wherein it is charged and discharged for the formation treatment of both the nickel and the hydrogen electrode plates.
Either of the above-mentioned sealed-type nickel-hydrogen cells shows its rated capacity at a low discharge rate such as 0.2.degree. C. when subjected to one to three cycles of the charge-discharge operation in the above-mentioned formation process. However, the discharge capacity a cell can provide at a 1C or higher discharge rate is much smaller, so that the cell has to be charged and discharged repeatedly for ten or more cycles in the formation process in order to increase the capacity. This charge-discharge operation when repeated such a large number of times makes the formation process considerably more troublesome and time-consuming and results in higher production costs and other disadvantages.